1. Field of the Invention
The present invention relates to an oxygen indicator for indicating the presence or absence of oxygen by changes in color. More particularly, this invention relates to an adhesive oxygen indicator which is in a chip shape having a self-adhesive surface on one side and which is used by attaching the self-adhesive surface to a deoxidizer package or the inside of a packaging container. Moreover, this invention relates to a deoxidizer package with an oxygen indicating function, to which the oxygen indicator has been pasted. Furthermore, this invention relates to a method and apparatus for fixing the oxygen indicator to an object.
2. Description of the Related Art
An oxygen indicator detects changes in oxygen concentration within a packaging container for food or the like. Specifically, the oxygen indicator indicates by changing its color that the oxygen within a package has been removed sufficiently by a deoxidizer. Examples of proposed forms of such oxygen indicator are: products molded into tablets; products obtained by impregnating paper, threads, absorbent cotton, resin moldings, and other porous substances with solutions of oxygen indicator compositions; and products obtained by applying or printing oxygen indicator compositions on the surface of paper or film. Such oxygen indicators are widely used, either in the form as they are or in the state packaged in laminated plastic films, primarily for preserving the quality of foods by using deoxidizers. Moreover, methods or structures for fixing the aforementioned oxygen indicator to a deoxidizer package or to the inside of a packaging container with an adhesive or a double-sided adhesive tape have also been proposed and implemented because such methods or structures have advantageous effects, for example, that the risk of the oxygen indicator being eaten by mistake will be eliminated.
For example, Japanese Patent Laid-Open (Kokai) Publication No. SHO 64-66561 discloses an oxygen indicator provided with: an oxygen indicator layer on at least one side of synthetic paper; a transparent layer over the oxygen indicator layer; and an adhesive layer on the entire or a part of the front side and;/or back side thereof. Japanese Utility Model Laid-Open (Kokai) Publication No. HEI 4-3980 proposes a method for making an integrated form of an oxygen indicator by pasting a sheet-shaped oxygen indicating agent to a deoxidizer packaging material with an adhesive or a double-sided adhesive tape. With these pasted oxygen indicators, however, moisture or oil contained in foods or other preserved products sometimes penetrates into the oxygen indicating agent and impairs their color changing function.
Moreover, Japanese Patent Laid-Open (Kokai) Publication No. HEI 8-282740 discloses an integrated oxygen indicating agent in which the following layers are laminated in the order as listed as follows: a deoxidizer package, a double-sided adhesive tape, an oxygen indicator sheet, and transparent film. However, since this integrated oxygen indicator uses the double-sided adhesive tape, the following problems take place: the obtained product is expensive; the oxygen indicator becomes thick and inflexible, thereby causing a sense of a cumbersome existence; and the productivity for making the integrated form is low. In addition, since only the peripheral portions of the oxygen indicator sheet are bonded to a transparent film, when the oxygen indicator and the transparent film are cut, there is a possibility that moisture or oil permeates through the cut edges of the indicator sheet and transparent film into the entire oxygen indicator sheet, causing abnormal changes in the color of the sheet.
Furthermore, a study conducted by the inventors of the present invention revealed that when deoxidizers are used in the packaging container of foods or the like, changes in the color of the oxygen indicator often lag behind changes in the oxygen concentration inside the packaging container. This results in a problem that the color changes of the oxygen indicator do not correspond to the changes in oxygen concentration.
A deoxidizer package is manufactured usually by packaging a deoxidizer with a packaging material having heat-sealability by means of heat sealing such as three-side sealing or four-side sealing. The deoxidizer package exhibits a function to absorb oxygen within a container and is used to maintain the freshness of foods packaged and to preserve pharmaceuticals. A deoxidizer package with an oxygen indicating function is also introduced, which is provided with the aforementioned oxygen indicator. This deoxidizer package with the oxygen indicating function is practically used as a product obtained by fixing a label-, sheet-, thread-, or plate-type oxygen indicator tape to the deoxidizer package with an adhesive or a double-sided adhesive tape.
Japanese Patent Laid-Open (Kokai) Publication No. HEI 8-275760 discloses a deoxidizer package with an oxygen indicating function, concerning which a thread-shaped oxygen indicator covered with a transparent adhesive tape is bonded to peripheral seal portions of the deoxidizer package, thereby it is possible to confirm color changes from any side, either front or back, of the deoxidizer package. However, since the edges of this integrated oxygen indicator are open, there is a problem in that moisture or oil contained in a preserved product such as foods penetrates into the thread-shaped oxygen indicator, thereby impairing the color changing function. Also, there is a problem in that loosen threads attach to the foods.
It is an object of the present invention to solve the above-described problems of the conventional oxygen indicators such as water/oil resistance and thickness as well as the cost problem, and to develop an adhesive oxygen indicator that has a wide range of uses and exhibits excellent color changing performance. Specifically, it is an object of this invention to provide an adhesive oxygen indicator that changes its color rapidly in response to changes in oxygen concentration, and to provide products in which this oxygen indicator is used. It is a still another object to solve the aforementioned problems and to provide a method and apparatus for fixing the new adhesive oxygen indicator as described above to objects such as deoxidizer packages, packaging pouches, small-pouch packages, packaging boxes, packaging cases, and packaged goods.
Furthermore, it is an object of this invention to develop a deoxidizer package with an oxygen indicating function, which can solve the aforementioned problems, which can be applied for a wide range of practical uses, which has excellent performance and safety, and which enables users to see the color changes of the oxygen indicator from either side of the deoxidizer package.
In order to achieve the above-described objects, this invention provides an oxygen indicator comprising:
an oxygen indicating agent including a substrate and an oxygen indicator composition fixed at the surface of the substrate; and
a single-sided self-adhesive plastic member having a self-adhesive layer on one side thereof,
wherein the oxygen indicating agent is provided over the single-sided self-adhesive plastic member by causing the oxygen indicator composition to closely contact the self-adhesive layer.
The single-sided self-adhesive plastic member is limitedly permeable to gas and moisture, and the single-sided self-adhesive plastic member is at least partly transparent. Furthermore, the width of the single-sided self-adhesive plastic member can be wider than that of the oxygen indicating agent and the oxygen indicating agent can be provided at an approximate center position in the width direction of the single-sided self-adhesive plastic member.
It is possible to employ such structure that the oxygen indicator composition is fixed at the surface of the substrate by means of application, printing, or impregnation.
The substrate and the single-sided self-adhesive plastic member can be formed in a strip shape, and a plurality of the oxygen indicator compositions can be fixed at regular intervals to the surface of the substrate and the respective oxygen indicator compositions can be made to closely contact the self-adhesive layer, thereby the respective oxygen indicating agents can be provided on the strip-shaped single-sided self-adhesive plastic member.
Moreover, a release member can be placed on the side of the single-sided self-adhesive plastic member where the self-adhesive layer is not provided.
Furthermore, the oxygen indicator of this invention can be used in the state of being cut into appropriate lengths.
The self-adhesive layer can be provided on the back side of the substrate and a release member can be provided thereon through the intermediary of the self-adhesive layer. This release member can be composed of release paper.
This invention also provides an oxygen indicator web comprising:
a plurality of oxygen indicators described above; and
a release member with the plurality of oxygen indicators provided thereon,
wherein the plurality of oxygen indicators are provided at regular intervals on the release member through the intermediary of the self-adhesive layer.
This invention provides a deoxidizer package with an oxygen indicating function, wherein the oxygen indicator described above is provided at a deoxidizer package containing a deoxidizer in a packaging material.
This invention also provides a deoxidizer package with an oxygen indicating function, wherein the above-described oxygen indicator web is provided at a deoxidizer package containing a deoxidizer in a packaging material.
The deoxidizer package is obtained by sealing at least a part of the packaging material containing the deoxidizer, and the oxygen indicator can be provided in the state of being held in the sealed portion. The oxygen indicator can be seen from either side of the deoxidizer package. Both sides of the deoxidizer package can be permeable to gas.
Moreover, this invention provides a method for manufacturing a deoxidizer package with an oxygen indicating function, comprising the steps of:
pasting the above-described oxygen indicator continuously to a packaged deoxidizer strip where a plurality of deoxidizer packages, which contain deoxidizers in packaging materials, are placed continuously, thereby forming a strip-shaped deoxidizer package with an oxygen indicating function; and
cutting the strip-shaped deoxidizer package with the oxygen indicating function to separate the continuous deoxidizer packages of the strip-shaped deoxidizer package with the oxygen indicating function into individual units.
This invention also provides a method for manufacturing a deoxidizer package with an oxygen indicating function, comprising the steps of:
pasting the above-described oxygen indicator web continuously to a packaged deoxidizer strip where a plurality of deoxidizer packages, which contain deoxidizers in packaging materials, are placed continuously, thereby forming a strip-shaped deoxidizer package with an oxygen indicating function; and
cutting the strip-shaped deoxidizer package with the oxygen indicating function to separate the continuous deoxidizer packages of the strip-shaped deoxidizer package with the oxygen indicating function into individual units.
Moreover, this invention provides a packaging IS container equipped with an oxygen indicator, wherein the above-described oxygen indicator is pasted to the interior of the packaging container.
Furthermore, this invention provides a method for fixing the above-described oxygen indicator to a strip-shaped object, wherein a self-adhesive tape, which has a self-adhesive layer formed thereon and which is at least partially transparent, is pasted to the strip-shaped object in a manner such that the oxygen indicator is interposed between this object and the self-adhesive tape.
This invention further provides a method for fixing, to a packaged deoxidizer strip where a plurality of deoxidizer packages containing deoxidizers are placed continuously, a tape-shaped oxygen indicator which comprises a tape-shaped oxygen indicating agent obtained by fixing an oxygen indicator composition to a tape-shaped substrate, and a single-sided self-adhesive plastic tape that is wider than the tape-shaped oxygen indicating agent, that is at least partially transparent, and that is provided with a self-adhesive layer on one side thereof, the tape-shaped oxygen indicating agent being adhesively attached to the approximate center (in the width direction) of the single-sided self-adhesive plastic tape,
wherein the parts of the single-sided self-adhesive plastic tape, which are devoid of the tape-shaped oxygen indicating agent, are pasted and fixed to the packaged deoxidizer strip.
This invention also provides a method for fixing, to a packaged deoxidizer strip where a plurality of deoxidizer packages containing deoxidizers are placed continuously, a tape-shaped oxygen indicator which comprises a tape-shaped oxygen indicating agent obtained by fixing an oxygen indicator composition to a tape-shaped substrate, and a single-sided self-adhesive plastic tape that is wider than the tape-shaped oxygen indicating agent, that is at least partially transparent, and that is provided with a self-adhesive layer on one side thereof, the tape-shaped oxygen indicating agent being adhesively attached to the approximate center (in the width direction) of the single-sided self-adhesive plastic tape,
wherein the method for fixing the tape-shaped oxygen indicator comprises the steps of:
interposing the tape-shaped oxygen indicating agent between the single-sided self-adhesive plastic tape and the packaged deoxidizer strip; and
pasting the self-adhesive layer of the single-sided self-adhesive plastic tape to the packaged deoxidizer strip, thereby pasting and fixing the interposed tape-shaped oxygen indicating agent to the packaged deoxidizer strip.
This invention also provides a fixing apparatus comprising:
a device for delivering a packaged deoxidizer strip where a plurality of deoxidizer packages containing deoxidizers are placed continuously;
a device for delivering a tape-shaped oxygen indicating agent, which is obtained by fixing an oxygen indicator composition to a tape-shaped substrate, toward the packaged deoxidizer strip;
a device for delivering a transparent film having a self-adhesive layer formed .on one side thereof toward the packaged deoxidizer strip; and
a device for pasting the self-adhesive layer of the transparent film to the packaged deoxidizer strip in a manner such that the tape-shaped oxygen indicating agent is interposed between the packaged deoxidizer strip and the transparent film.
This invention further provides an apparatus for fixing, to a packaged deoxidizer strip where a plurality of deoxidizer packages containing deoxidizers are placed continuously, a tape-shaped oxygen indicator which comprises a tape-shaped oxygen indicating agent obtained by fixing an oxygen indicator composition to a tape-shaped substrate, and a single-sided self-adhesive plastic tape that is at least partially transparent and that is provided with a self-adhesive layer on one side thereof, the tape-shaped oxygen indicating agent being directly attached to the single-sided self-adhesive plastic tape, wherein the apparatus for fixing the tape-shaped oxygen indicator comprises: a device for continuously delivering the packaged deoxidizer strip; a device for continuously delivering the tape-shaped oxygen indicating agent toward the packaged deoxidizer strip; a device for delivering the single-sided self-adhesive plastic tape toward the packaged deoxidizer strip; and a device for pasting the self-adhesive layer of the single-sided self-adhesive plastic tape to the packaged deoxidizer strip in a manner such that the tape-shaped oxygen indicating agent is interposed between the single-sided self-adhesive plastic tape and the packaged deoxidizer strip.
Concerning this fixing apparatus, the single-sided self-adhesive plastic tape is wider than the tape-shaped oxygen indicating agent, and the device for pasting the self-adhesive layer of the single-sided self-adhesive plastic tape to the packaged deoxidizer strip is configured in a manner such that on the surface of the single-sided self-adhesive plastic tape where the self-adhesive layer thereof is formed, both side margins (in the width direction) of the single-sided self-adhesive plastic tape constitute the parts devoid of the tape-shaped oxygen indicating agent so that the tape-shaped oxygen indicating agent is located in the approximate center (in the width direction) of the single-sided self-adhesive plastic tape, and such parts devoid of the, tape-shaped oxygen indicating agent can be pasted to the packaged deoxidizer strip.
Alternatively, a self adhesive layer is provided on the back side of the substrate and a release member is provided on the self-adhesive layer. In this case, the oxygen indicator can be fixed to the deoxidizer package through the intermediary of, the self-adhesive layer.
The above-described oxygen indicating agent can be obtained by applying or printing a plurality of oxygen indicator compositions, either at regular intervals or continuously, on one side of a limitedly moisture-permeable plastic film or synthetic paper.
Concerning the above-described method, the object can be composed of a packaged deoxidizer strip where a plurality of deoxidizer packages containing deoxidizers are placed continuously, and the above-described method can further comprise the step of pasting the oxygen indicating agent and the self-adhesive tape to the packaged deoxidizer strip and then cutting the obtained strip to separate the respective deoxidizer packages into individual units.
Concerning the above-described apparatus, the object can be composed of a packaged deoxidizer strip where a plurality of deoxidizer packages containing deoxidizers are placed continuously, and the apparatus can further comprise the device of pasting the oxygen indicating agent and the self-adhesive tape to the packaged deoxidizer strip and then cutting the obtained strip to separate the respective deoxidizer packages into individual units.
The term xe2x80x9ctape shapexe2x80x9d used in relation to this invention refers to the shape of which length is greater than its width and of which thickness is less than its width. The oxygen indicator of this invention should have a thickness of 2 mm or less, more preferably 0.5 mm or less, and should have a width ranging from 3 mm to 30 mm. Although the length of the oxygen indicator is not specifically limited because it can be cut in an appropriate size at the time of pasting and then be used, it is desirable that the length of the oxygen indicator be at least several tens of meters, which will enable continuous processing, in order to minimize the costs for manufacturing and,for the use of the oxygen indicator.
The oxygen indicator of this invention has a very simple structure which basically comprises an oxygen indicating agent and a single-sided self-adhesive plastic tape. Accordingly, the productivity is high and it is possible to reduce the costs. In addition, the operability at the time of use is high, thereby making it possible to reduce the total costs required for the oxygen indicator.
Moreover, the single-sided self-adhesive tape adopts a reasonable layer structure such that the oxygen indicator composition surface of the oxygen indicating agent is sealed in the approximate central portion of the single-sided self-adhesive tape and the margin portions of the tape edges are used for adhesive attachment and pasting. Accordingly, the resultant oxygen indicator of this invention is thin and highly flexible, has excellent color changing performance and water and oil resistance as an oxygen indicator, and exhibits good oxygen indicating performance without suffering deterioration in performance even under the rigorous working conditions of high humidity. Because of its excellent flexibility, the oxygen indicator can exhibit its adherence capability to uneven or low-rigidity surfaces of deoxidizer packages or food-containing packaging containers.
When the oxygen indicator of this invention is used, one surface of the oxygen indicator composition is covered with the single-sided self-adhesive tape, and the opposite surface is separated and hermetically sealed by the substrate from the outside atmosphere. However, as compared with a conventional type of oxygen indicator of which oxygen indicator composition is exposed to the outside atmosphere, the oxygen indicator of this invention shows a higher color change rate in response to a decrease in the oxygen concentration within the outside atmosphere. Although the mechanism of this phenomenon is not yet clear, it might be attributed to the fact that the single-sided self-adhesive tape prevents excessive absorption of moisture (which causes deterioration of the oxygen indicating performance) and has a function of adequately transmitting the atmospheric: gas, and that the oxygen indicator composition is sealed without leaving any void, thereby preventing the oxygen indicator components from transferring to the outside.
The oxygen indicating agent of this invention is made by pasting the oxygen indicator composition to the substrate and indicates the existence or absence of oxygen as the oxygen indicator composition changes its color according to the oxygen concentration in the ambient atmosphere.
As the oxygen indicator composition, compositions containing the following substances as essential components are preferably used: dyes which show color changes with a reducing agent such as anthraquinone dye, indigo dye, or thiazine dye, or sulfur dye; alkali substances such as hydroxides or salts of alkali metals or alkaline earth metals; and reducing agents: such as reducing sugar. In addition to these essential components, a solvent, a dye or pigment which does not change color even with the existence of the reducing agent, a water soluble high polymer, a binder resin, and other substances are combined and added as necessary, and the obtained composition is then attached to the tape-shaped substrate. Examples of the method of attachment include application, printing, and impregnation.
As for the label-shaped oxygen indicating agent, in order to exhibit high oxygen indicating performance even under severe conditions of high humidity, such oxygen indicating agent is preferably used that is obtained by applying or printing the oxygen indicator composition onto one side of limitedly gas- and moisture-permeable synthetic paper or film.
A limitedly gas- and moisture-permeable synthetic paper or film is used as the substrate. Examples of such materials include polyethylene, polypropylene, polyester, polyamide, polycarbonate, cellulose acetate, and cellophane. Oriented polypropylene or polyester is preferred from the standpoint of transparency, flexibility, strength, and the like. No particular limitations are imposed on the thickness of the substrate as long as practical strength and flexibility are obtained, but a thickness of 10-100 microns is preferred. In addition, the oxygen permeability of the label substrate should preferably be 50-3000 cc/m2xc2x7dayxc2x7atm, and moisture permeability should preferably be 50 g/m2xc2x7day or lower.
It is desirable that this substrate be opaque or be appropriately colored in order to make the color changes of the oxygen indicating agent more visible. Moreover, it is possible to leave a part of the substrate transparent so that the color changes of the oxygen indicator can be observed, while using the remaining parts for displaying information such as characters or pictorial symbols for concealment, and it is also possible to print the substrate with an appropriate color in order to make it easier to distinguish the color of the oxygen indicating agent.
The oxygen indicating agent on the substrate should be so large that it is visible from either side of the deoxidizer package, when the oxygen indicator is pasted in a manner that the oxygen indicator encloses the seal portion of the deoxidizer package. Specifically, the oxygen indicating agent on the substrate forms a continuous or continual belt shape of the width of more than 2 mm, preferably 4-20 mm, or a circle or oval shape of the diameter of more than 2 mm, preferably 4-20 mm.
The single-sided self adhesive tape as described above is obtained preferably by applying or laminating an adhesive over one side of a plastic film. Examples of materials for the plastic film include polyethylene, polypropylene, polyester, polyamide, polycarbonate, cellulose acetate, and cellophane. Polypropylene, polyester or polyamide is preferred. Oriented polypropylene or polyester is more preferred from the standpoint of transparency, flexibility, and strength. No particular limitations are imposed on the thickness of the plastic film as long as practical strength and flexibility are obtained, but a thickness of 10-100 microns is preferred. The plastic film may either be colorless and transparent or be appropriately colored and transparent in order to make the color changes of the oxygen indicating agent more visible. Moreover, it is possible to leave a part of the plastic film transparent so that the color changes of the oxygen indicating agent can be observed, while using the remaining parts of the plastic film for displaying information such as characters or pictorial symbols for concealment, and it is also possible to print the plastic film with an appropriate color in order to make it easier to distinguish the color of the oxygen indicating agent. In addition, the oxygen permeability of the plastic film should preferably be 50-3000 cc/m2xc2x7dayxc2x7atm, and moisture permeability should preferably be 50 g/m2xc2x7day or lower.
As examples of materials composing the self-adhesive layer, the following materials can be used: synthetic rubbers, natural rubbers, acrylics, silicones, and other known materials. It is desirable that the self-adhesive layer be applied to or laminated over the entire surface of one side of the plastic film. In this case, the type and thickness of the self-adhesive layer may be selected as appropriate in consideration of the following points that the pigment used for the oxygen indicating agent will not stain or the color changes of the pigment will not be inhibited, that the self-adhesive layer should have excellent transparency, that the self-adhesive layer should be highly stable and hygienic, and that appropriate adhesion to an adherend should be achieved.
This self-adhesive layer can be formed by various methods, including: a method of applying an adhesive as an emulsion or a solution diluted with a solvent to a base, which composes the single-sided self-adhesive plastic tape, and then drying the applied adhesive; a method of extruding and laminating an adhesive to the base; and a method of transferring an adhesive, which has been formed in a film shape, from release paper to the base.
This invention realizes better water and oil resistance by covering the oxygen indicator composition with the single-sided self-adhesive plastic tape which is limitedly permeable to gas and moisture and is transparent. Accordingly, it is desirable that the entire oxygen indicator composition be in direct contact with the self-adhesive layer substantially without leaving any void or the substantially entire adhesive surface of the oxygen indicating agent is sealed by the self-adhesive tape.
The oxygen indicator of this invention can be made in a label which is thin and in a chip shape. Accordingly, such oxygen indicator will hardly decrease the capabilities of a deoxidizer and it will not cause any sense of a cumbersome existence when integrated with a deoxidizer. In addition, since the oxygen indicator has the self-adhesive surface on the back side, it hardly comes off. Since the oxygen indicator is covered!with the single-sided self-adhesive plastic tape which is limitedly permeable to gas and moisture and is transparent, the oxygen indicator is resistant to water and oil.
Moreover, a plurality of the oxygen indicators of this invention can be formed into a web where the oxygen indicators are pasted with their self-adhesive surfaces on their back sides to release paper, the oxygen indicator can be readily used for pasting when it is peeled off from the release paper. Therefore, manufacturing costs are reduced and high-speed pasting can be performed by using an automatic pasting machine, thereby improving the productivity.